U.S. patent application number 13/479461 was filed with the patent office on 2012-09-13 for battery.
This patent application is currently assigned to SONY CORPORATION. Invention is credited to Hiroyuki Akashi, Tomitaro Hara, Yosuke Hosoya, Yoshiaki Obana, Kenichi Ogawa.
Application Number | 20120231347 13/479461 |
Document ID | / |
Family ID | 37070911 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120231347 |
Kind Code |
A1 |
Hara; Tomitaro ; et
al. |
September 13, 2012 |
BATTERY
Abstract
A battery capable of improving the energy density and improving
the cycle characteristics is provided. The battery includes a
cathode, an anode arranged opposite of the cathode and an
electrolyte in between the cathode and the anode. The amount of
cathode active material and the amount of anode active material is
such that the open circuit battery voltage is within the range from
4.25 volts to 6.00 volts, the electrolyte contains an electrolytic
solution and a polymer containing vinylidene fluoride, and the
cathode contains lithium complex oxides.
Inventors: |
Hara; Tomitaro; (Fukushima,
JP) ; Akashi; Hiroyuki; (Kanagawa, JP) ;
Ogawa; Kenichi; (Fukushima, JP) ; Obana;
Yoshiaki; (Fukushima, JP) ; Hosoya; Yosuke;
(Fukushima, JP) |
Assignee: |
SONY CORPORATION
Tokyo
JP
|
Family ID: |
37070911 |
Appl. No.: |
13/479461 |
Filed: |
May 24, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11278576 |
Apr 4, 2006 |
|
|
|
13479461 |
|
|
|
|
Current U.S.
Class: |
429/316 |
Current CPC
Class: |
H01M 10/4235 20130101;
H01M 4/525 20130101; H01M 4/582 20130101; H01M 10/052 20130101;
H01M 10/0565 20130101; Y02E 60/10 20130101; H01M 4/505 20130101;
H01M 2300/0085 20130101 |
Class at
Publication: |
429/316 |
International
Class: |
H01M 10/02 20060101
H01M010/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2005 |
JP |
2005-107784 |
Jul 29, 2005 |
JP |
2005-222038 |
Claims
1. A battery comprising: a cathode; an anode arranged opposite of
the cathode; and an electrolyte in between the cathode and the
anode, wherein, the amount of cathode active material and the
amount of anode active material is such that the open circuit
battery voltage is within the range from 4.25 volts to 6.00 volts,
the electrolyte contains an electrolytic solution and a polymer
containing vinylidene fluoride, the cathode contains lithium
complex oxides represented by chemical formula 3:
Li.sub.rCo.sub.(1-s)M3.sub.sO.sub.(2-t)F.sub.u, where M3 represents
at least one element selected from the group consisting of nickel,
manganese, magnesium, aluminum, boron, titanium, vanadium,
chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium
and tungsten, r, s, t and u are values in the range of
0.8.ltoreq.r.ltoreq.1.2, 0<s<0.5, -0.1.ltoreq.t.ltoreq.0.2,
and 0.ltoreq.u.ltoreq.0.1.
2. The battery according to claim 1, wherein the polymer contains a
copolymer containing vinylidene fluoride and
hexafluoropropylene.
3. The battery according to claim 2, wherein the copolymerization
amount of hexafluoropropylene in the copolymer is 7 wt % or less.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/278,576, filed Apr. 6, 2006 the entirety of
which is incorporated herein by reference to the extent permitted
by law. The present invention claims priority to Japanese Patent
Applications JP 2005-107784 filed in the Japanese Patent Office on
Apr. 4, 2005 and JP2005-222038 filed in the Japanese Patent Office
on Jul. 29, 2005, which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a battery, in which the
open circuit voltage in a full charge state per a pair of the
cathode and the anode is 4.25 V or more.
[0004] 2. Description of the Related Art
[0005] In recent years, many portable electronic devices such as
combination cameras, mobile phones, and portable computers have
been introduced, and their size and weight have been reduced. In
these electronic devices, in addition to the size reduction,
multifunction and sophistication have been promoted. In the result,
the power consumption thereof is not always lowered. In practice,
the usage time tends to become longer because of the multifunction.
Users desire to use such portable electronic devices for a longer
time. Accordingly, a higher energy density of lithium ion secondary
batteries widely used as a power source for the portable electronic
devices has been desired.
[0006] In general, in traditional lithium ion secondary batteries,
lithium cobaltate is used for the cathode, a carbon material is
used for the anode, and the operating voltage is in the range from
4.2 V to 2.5 V. In such a lithium ion secondary batteries operating
at 4.2 V at maximum, for the cathode active material such as
lithium cobaltate used for the cathode, only about 60% of the
theoretical capacity is utilized. Therefore, in principle, it is
possible to utilize the remaining capacity by further increasing
the charging voltage. In fact, it is known that a high energy
density is realized by setting the voltage in charging to 4.25 V or
more (refer to International Publication No. WO03/0197131).
SUMMARY OF THE INVENTION
[0007] However, in the battery setting the charging voltage over
4.2 V, oxidative atmosphere particularly in the vicinity of the
cathode surface is intensified. In the result, the nonaqueous
electrolyte material and the separator, which physically contact
the cathode, are easily oxidized and decomposed. Thereby, there is
a disadvantage that the internal resistance is increased, and the
battery characteristics such as cycle characteristics are
lowered.
[0008] Disclosed herein are one or more inventions, the embodiments
of which address the problems discussed above.
[0009] According to an embodiment, there is provided a battery in
which a cathode and an anode are oppositely arranged with an
electrolyte in between, wherein an open circuit voltage in a full
charge state per a pair of the cathode and the anode is in the
range from 4.25 V to 6.00 V, and the electrolyte contains an
electrolytic solution and a polymer containing vinylidene fluoride
as a component.
[0010] According to the battery of another embodiment since the
open circuit voltage in a full charge state per a pair of the
cathode and the anode is in the range from 4.25 V to 6.00 V, a high
energy density can be obtained. Further, since the electrolyte
contains a polymer containing vinylidene fluoride as a component,
oxidation and decomposition reaction in the vicinity of the cathode
surface can be inhibited, and the battery characteristics such as
cycle characteristics can be improved.
[0011] Other and further objects, features and advantages of the
invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is an exploded perspective view showing a structure
of a secondary battery according to an embodiment of the present
invention;
[0013] FIG. 2 is a cross section taken along line I-I of a spirally
wound electrode body shown in FIG. 1;
[0014] FIG. 3 is a characteristics diagram showing a relation
between cycle number and discharge capacity retention ratio when a
charging voltage is 4.25 V;
[0015] FIG. 4 is a characteristics diagram showing a relation
between cycle number and discharge capacity retention ratio when a
charging voltage is 4.55 V;
[0016] FIG. 5 is a characteristics diagram showing a relation
between cycle number and discharge capacity retention ratio when a
charging voltage is 4.20 V;
[0017] FIG. 6 is a characteristics diagram showing a relation
between cycle number and discharge capacity retention ratio
according to charging voltage;
[0018] FIG. 7 is another characteristics diagram showing a relation
between cycle number and discharge capacity retention ratio
according to charging voltage;
[0019] FIG. 8 is still another characteristics diagram showing a
relation between cycle number and discharge capacity retention
ratio according to charging voltage; and
[0020] FIG. 9 is still another characteristics diagram showing a
relation between cycle number and discharge capacity retention
ratio according to charging voltage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] An embodiment of the present invention will be hereinafter
described in detail with reference to the drawings.
[0022] FIG. 1 shows a structure of a secondary battery according to
an embodiment of the present invention. In the secondary battery,
lithium (Li) is used as an electrode reactant. For example, the
secondary battery has a structure in which a spirally wound
electrode body 10 on which a cathode lead 11 and an anode lead 12
are attached is contained inside a film package member 20.
[0023] The cathode lead 11 and the anode lead 12 are respectively
directed from inside to outside of the package member 20 in the
same direction, for example. The cathode lead 11 and the anode lead
12 are respectively made of, for example, a metal material such as
aluminum (Al), copper (Cu), nickel (Ni), and stainless, and are in
the shape of thin plate or mesh.
[0024] The package member 20 is made of a rectangular aluminum
laminated film in which, for example, a nylon film, an aluminum
foil, and a polyethylene film are bonded together in this order.
The package member 20 is, for example, arranged so that the
polyethylene film side and the spirally wound electrode body 10 are
opposed, and the respective outer edges are contacted to each other
by fusion bonding or an adhesive. Adhesive films 21 to protect from
outside air intrusion are inserted between the package member 20
and the cathode lead 11, the anode lead 12. The adhesive film 21 is
made of a material having contact characteristics to the cathode
lead 11 and the anode lead 12, for example, is made of a polyolefin
resin such as polyethylene, polypropylene, modified polyethylene,
and modified polypropylene.
[0025] The exterior member 20 may be made of a laminated film
having other structure, a high molecular weight film such as
polypropylene, or a metal film, instead of the foregoing aluminum
laminated film.
[0026] FIG. 2 shows a cross sectional structure taken along line
I-I of the spirally wound electrode body 10 shown in FIG. 1. In the
spirally wound electrode body 10, a pair of a cathode 13 and an
anode 14 is layered with a separator 15 and an electrolyte 16 in
between and wound. The cathode 13 and the anode 14 are oppositely
arranged with the separator 15 and the electrolyte 16 in between.
The outermost periphery of the spirally wound electrode body 10 is
protected by a protective tape 17.
[0027] The cathode 13 has a structure in which, for example, a
cathode active material layer 13B is provided on the both faces of
a cathode current collector 13A having a pair of opposed faces.
Though not shown, the cathode active material layer 13B may be
provided on only one face of the cathode current collector 13A. The
cathode current collector 13A is made of a metal foil such as an
aluminum foil, a nickel foil, and a stainless foil. The cathode
active material layer 13B contains, for example, as a cathode
active material, one or more cathode materials capable of inserting
and extracting lithium, which is an electrode reactant. If
necessary, the cathode active material layer 13B contains an
electrical conductor such as graphite and a binder such as
polyvinylidene fluoride.
[0028] As a cathode material capable of inserting and extracting
lithium, for example, a lithium-containing compound such as a
lithium oxide, a lithium phosphorous oxide, a lithium sulfide, and
an intercalation compound containing lithium is appropriate. Two or
more thereof may be used by mixing. In order to improve the energy
density, a lithium-containing compound which contains lithium,
transition metal elements, and oxygen (O) is preferable. Specially,
a lithium-containing compound which contains at least one from the
group consisting of cobalt (Co), nickel, manganese (Mn), and iron
(Fe) as a transition metal element is more preferable. As such a
lithium-containing compound, for example, a bedded salt type
lithium complex oxide shown in Chemical formula 1, Chemical formula
2, or Chemical formula 3; a spinel type lithium complex oxide shown
in Chemical formula 4; an olivine type lithium complex phosphate
shown in Chemical formula 5 or the like can be cited. Specifically,
LiNi.sub.0.50CO.sub.0.20Mn.sub.0.30O.sub.2, Li.sub.aCoO.sub.2
(a.apprxeq.1), Li.sub.bNiO.sub.2 (b.apprxeq.1),
Li.sub.c1Ni.sub.c2Co.sub.1-c2O.sub.2 (c1.apprxeq.1, 0<c2<1),
Li.sub.dMn.sub.2O.sub.4 (d.apprxeq.1), Li.sub.eFePO.sub.4
(e.apprxeq.1) or the like can be cited.
Li.sub.fMn.sub.(1-g-h)Ni.sub.gM1.sub.hO.sub.(2-j)F.sub.k (Chemical
formula 1)
[0029] In the formula, M1 represents at least one from the group
consisting of cobalt, magnesium (Mg), aluminum, boron (B), titanium
(Ti), vanadium (V), chromium (Cr), iron, copper, zinc (Zn),
zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium
(Sr), and tungsten (W). f, g, h, j, and k are values in the range
of 0.8.ltoreq.f.ltoreq.1.2, 0<g<0.5, 0.ltoreq.h.ltoreq.0.5,
g+h<1, -0.1.ltoreq.j.ltoreq.0.2, and 0.ltoreq.k.ltoreq.0.1. The
composition of lithium varies according to charge and discharge
states. A value off represents the value in a full discharge
state.
Li.sub.mNi.sub.(1-n)M2.sub.nO.sub.(2-p)F.sub.q (Chemical formula
2)
[0030] In the formula, M2 represents at least one from the group
consisting of cobalt, manganese, magnesium, aluminum, boron,
titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin,
calcium, strontium, and tungsten. m, n, p, and q are values in the
range of 0.8.ltoreq.m.ltoreq.1.2, 0.005.ltoreq.n.ltoreq.0.5,
-0.1.ltoreq.p.ltoreq.0.2, and 0.ltoreq.q.ltoreq.0.1. The
composition of lithium varies according to charge and discharge
states. A value of m represents the value in a full discharge
state.
Li.sub.rCO.sub.(1-s)M3.sub.sO.sub.(2-t)F.sub.u (Chemical formula
3)
[0031] In the formula, M3 represents at least one from the group
consisting of nickel, manganese, magnesium, aluminum, boron,
titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin,
calcium, strontium, and tungsten. r, s, t, and u are values in the
range of 0.8.ltoreq.r.ltoreq.1.2, 0.ltoreq.s<0.5,
-0.1.ltoreq.t.ltoreq.0.2, and 0.ltoreq.u.ltoreq.0.1. The
composition of lithium varies according to charge and discharge
states. A value of r represents the value in a full discharge
state.
Li.sub.vMn.sub.2-wM4.sub.wO.sub.xF.sub.y (Chemical formula 4)
[0032] In the formula, M4 represents at least one from the group
consisting of cobalt, nickel, magnesium, aluminum, boron, titanium,
vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium,
strontium, and tungsten. v, w, x, and y are values in the range of
0.9.ltoreq.v.ltoreq.1.1, 0.ltoreq.w.ltoreq.0.6,
3.7.ltoreq.x.ltoreq.4.1, and 0.ltoreq.y.ltoreq.0.1. The composition
of lithium varies according to charge and discharge states. A value
of v represents the value in a full discharge state.
Li.sub.zM5PO.sub.4 (Chemical formula 5)
[0033] In the formula, M5 represents at least one from the group
consisting of cobalt, manganese, iron, nickel, magnesium, aluminum,
boron, titanium, vanadium, niobium, copper, zinc, molybdenum,
calcium, strontium, tungsten, and zirconium. z is a value in the
range of 0.9.ltoreq.z.ltoreq.1.1. The composition of lithium varies
according to charge and discharge states. A value of z represents
the value in a full discharge state.
[0034] As a cathode material capable of inserting and extracting
lithium, in addition to the foregoing, an inorganic compound not
containing lithium such as MnO.sub.2, V.sub.2O.sub.5,
V.sub.6O.sub.13, NiS, and MoS can be cited.
[0035] The anode 14 has a structure in which an anode active
material layer 14B is provided on the both faces of an anode
current collector 14A having a pair of opposed faces. Though not
shown, the anode active material layer 14B may be provided only on
one face of the anode current collector 14A. The anode current
collector 14A is made of, for example, a metal foil such as a
copper foil, a nickel foil, and a stainless foil, which have
favorable electrochemical stability, electrical conductivity, and
mechanical strength. In particular, the copper foil is most
preferable, since the copper foil has high electrical
conductivity.
[0036] The anode active material layer 14B contains, as an anode
active material, one or more anode materials capable of inserting
and extracting lithium. If necessary, the anode active material
layer 14B contains a binder similar to of the cathode active
material layer 13B.
[0037] As an anode material capable of inserting and extracting
lithium, for example, a carbon material such as non-graphitizable
carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes,
glassy carbons, an organic high molecular weight compound fired
body, carbon fiber, and activated carbon can be cited. Of the
foregoing, cokes include pitch cokes, needle cokes, petroleum cokes
and the like. The organic high molecular weight compound fired body
is obtained by firing and carbonizing a high molecular weight
material such as a phenol resin and a furan resin at appropriate
temperatures, and some thereof are categorized as non-graphitizable
carbon or graphitizable carbon. As a high molecular weight
material, polyacetylene, polypyrrole or the like can be cited.
These carbon materials are preferable, since the crystal structure
change generated in charge and discharge is very small, a high
charge and discharge capacity can be obtained, and favorable cycle
characteristics can be obtained. In particular, graphite is
preferable, since the electrochemical equivalent is large, and a
high energy density can be obtained. Further, non-graphitizable
carbon is preferable since superior characteristics can be
obtained. Furthermore, a material with a low charge and discharge
potential, specifically a material with the charge and discharge
potential close to of lithium metal is preferable, since a high
energy density of the battery can be thereby easily realized.
[0038] As an anode material capable of inserting and extracting
lithium, a material, which is capable of inserting and extracting
lithium, and contains at least one of metal elements and metalloid
elements as an element can be also cited. When such a material is
used, a high energy density can be obtained. In particular, such a
material is more preferably used together with a carbon material,
since a high energy density can be obtained, and superior cycle
characteristics can be obtained. Such an anode material may be a
simple substance, an alloy, or a compound of a metal element or a
metalloid element, or may have one or more phases thereof at least
in part. In the present invention, alloys include an alloy
containing one or more metal elements and one or more metalloid
elements, in addition to an alloy including two or more metal
elements. Further, an alloy may contain nonmetallic elements. The
texture thereof includes a solid solution, a eutectic crystal
(eutectic mixture), an intermetallic compound, and a texture in
which two or more thereof coexist.
[0039] As a metal element or a metalloid element composing the
anode material, magnesium, boron, aluminum, gallium (Ga), indium
(In), silicon (Si), germanium (Ge), tin, lead (Pb), bismuth (Bi),
cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium
(Y), palladium (Pd), or platinum (Pt) can be cited. They may be
crystalline or amorphous.
[0040] Specially, as the anode material, a material containing a
metal element or a metalloid element of Group 4B in the short
period periodic table as an element is preferable. A material
containing at least one of silicon and tin as an element is
particularly preferable. Silicon and tin have a high ability to
insert and extract lithium, and can provide a high energy
density.
[0041] As an alloy of tin, for example, an alloy containing at
least one from the group consisting of silicon, nickel, copper,
iron, cobalt, manganese, zinc, indium, silver, titanium, germanium,
bismuth, antimony (Sb), and chromium as a second element other than
tin can be cited. As an alloy of silicon, for example, an alloy
containing at least one from the group consisting of tin, nickel,
copper, iron, cobalt, manganese, zinc, indium, silver, titanium,
germanium, bismuth, antimony, and chromium as a second element
other than silicon can be cited.
[0042] As a compound of tin or a compound of silicon, for example,
a compound containing oxygen or carbon (C) can be cited. In
addition to tin or silicon, the compound may contain the foregoing
second element.
[0043] As an anode material capable of inserting and extracting
lithium, other metal compound or a high molecular weight material
can be further cited. As other metal compound, an oxide such as
MnO.sub.2, V.sub.2O.sub.5, and V.sub.6O.sub.13; a sulfide such as
NiS and MoS; or a lithium nitride such as LiN.sub.3 can be cited.
As a high molecular weight material, polyacetylene, polyaniline,
polypyrrole or the like can be cited.
[0044] Further, in the secondary battery, the open circuit voltage
in full charge (that is, battery voltage) is designed to fall
within the range from 4.25 V to 6.00 V by adjusting the amounts of
the cathode active material and the anode active material. Thereby,
a high energy density can be obtained. For example, in the case
that the open circuit voltage in full charge is 4.25 V or more, the
lithium extraction amount per unit weight becomes larger than in
the battery with the open circuit voltage in full charge of 4.2 V
even though the same cathode active material is used. Accordingly,
the amount of the anode active material is adjusted.
[0045] The separator 15 is made of a porous film made of a
synthetic resin such as polytetrafluoroethylene, polypropylene, and
polyethylene, or a ceramics porous film. The separator 15 may have
a structure in which two or more porous films as the foregoing
porous films are layered. Specially, the polyolefin porous film is
preferable, since such a film has superior short circuit prevention
effect and can improve battery safety by shutdown effect.
[0046] The electrolyte 16 contains an electrolytic solution and a
high molecular weight compound holding the electrolytic solution,
and is so-called gelatinous. The electrolytic solution contains a
solvent and an electrolyte salt.
[0047] As a solvent, for example, a nonaqueous solvent such as
lactone such as .gamma.-butyrolactone, .gamma.-valerolactone,
.delta.-valerolactone, and .epsilon.-caprolactone; ester carbonate
such as ethylene carbonate, propylene carbonate, butylene
carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl
carbonate, and diethyl carbonate; ether such as 1,2-dimethoxy
ethane, 1-ethoxy-2-methoxy ethane, 1,2-diethoxy ethane,
tetrahydrofuran, and 2-methyl tetrahydrofuran; ester such as methyl
propionate; sulfoxide such as dimethyl sulfoxide; nitrile such as
acetonitrile; sulfolane; phosphoric acids; phosphoric ester;
pyrrolidone; and their derivatives can be cited. One of the
solvents may be used singly, or two or more thereof may be used by
mixing.
[0048] For the electrolyte salt, for example, a lithium salt can be
cited. One of lithium salts may be used singly, or two or more
thereof may be used by mixing. As a lithium salt, LiPF.sub.6,
LiBF.sub.4, LiAsF.sub.6, LiClO.sub.4, LiClO.sub.3, LiBrO.sub.3,
LiIO.sub.3, LiNO.sub.3, LiCH.sub.3COO, LiB(C.sub.6H.sub.5).sub.4,
LiCH.sub.3SO.sub.3, LiCF.sub.3SO.sub.3,
LiN(SO.sub.2CF.sub.3).sub.2, LiC(SO.sub.2CF.sub.3).sub.3,
LiAlCl.sub.4, LiSiF.sub.6, LiCl, LiBr, LiI, difluoro
[oxolate-O--O']lithium borate, lithium bis oxalate borate or the
like can be cited. Specially, LiPF.sub.6 and LiBF.sub.4 are
preferable, since LiPF.sub.6 and LiBF.sub.4 have high oxidation
stability.
[0049] The high molecular weight compound contains a polymer
containing vinylidene fluoride as a component. Thereby, the
oxidation stability of the electrolyte 16 can be improved, and
oxidation and decomposition reaction in the vicinity of the cathode
13 can be inhibited even when the battery voltage is raised. The
polymer may be polyvinylidene fluoride or a copolymer containing
vinylidene fluoride as a component. One polymer may be used singly,
or two or more polymers may be used by mixing. Further, other one
or more high molecular weight compound may be mixed with the
polymer containing vinylidene fluoride as a component.
[0050] As a copolymer containing vinylidene fluoride as a
component, a copolymer containing, for example,
hexafluoropropylene, monoester of unsaturated dibasic acid such as
monomethyl ester maleate, ethylene halide such as ethylene chloride
trifluoride, cyclic ester carbonate of unsaturated compound such as
vinylene carbonate, or epoxy group containing acryl vinyl monomer
as other component can be cited. Other component may be one or
more.
[0051] Specially, as the polymer, a copolymer containing vinylidene
fluoride and hexafluoropropylene as a component is preferable. Such
a copolymer has high contact characteristics and impregnation
characteristics to the electrode, and provides superior battery
characteristics. In particular, the block copolymer thereof is
preferable, since such a block copolymer can provide high
characteristics. The copolymerization amount of hexafluoropropylene
in the copolymer is preferably 7 wt % or less. When the
copolymerization amount of hexafluoropropylene is too large,
crystallinity of the base material polymer is changed, and the
mechanical strength and the ability of holding the electrolytic
solution are lowered.
[0052] The electrolyte 16 is preferably sandwiched at least between
the cathode 13 and the separator 15. As described above, the
electrolyte 16 has high oxidation stability since the electrolyte
16 contains a polymer containing vinylidene fluoride as a
component. Therefore, the electrolyte 16 can inhibit the separator
15 from being contacted with the cathode 13 and oxidized and
decomposed. In this embodiment, as shown in FIG. 2, the electrolyte
16 is provided between the cathode 13 and the separator 15, and
between the anode 14 and the separator 15, respectively.
[0053] The secondary battery can be manufactured, for example, as
follows.
[0054] First, for example, the cathode 13 is formed by forming the
cathode active material layer 13B on the cathode current collector
13A. The cathode active material layer 13B is formed, for example,
as follows. A cathode material capable of inserting and extracting
lithium, an electrical conductor, and a binder are mixed to prepare
a cathode mixture, which is dispersed in a solvent such as
N-methyl-2-pyrrolidone to obtain a paste cathode mixture slurry.
Then, the cathode current collector 13A is coated with the cathode
mixture slurry, the solvent is dried, and the resultant is
compression-molded by a rolling press machine. Consequently, the
cathode active material layer 13B is formed.
[0055] Further, for example, the anode 14 is formed by forming the
anode active material layer 14B on the anode current collector 14A.
The anode active material layer 14B may be formed by, for example,
any of vapor-phase deposition method, liquid-phase deposition
method, firing method, coating, and combination of two or more of
these methods. As vapor-phase deposition method, for example,
physical deposition method or chemical deposition method can be
used. Specifically, vacuum vapor deposition method, sputtering
method, ion plating method, laser ablation method, thermal CVD
(Chemical Vapor Deposition) method, plasma CVD method and the like
are available. As liquid-phase deposition method, a known technique
such as electrolytic plating and electroless plating is available.
For firing method, a known technique such as atmosphere firing
method, reactive firing method, and hot press firing method is
available. In the case of coating, the anode active material layer
14B can be formed in the same manner as in the cathode 13.
[0056] Next, the electrolyte 16 is formed by coating the cathode 13
and the anode 14 with a precursor solution containing an
electrolytic solution, a high molecular weight compound, and a
mixed solvent, and then volatilizing the mixed solvent. After that,
the cathode lead 11 is attached to the cathode current collector
13A, and the anode lead 12 is attached to the anode current
collector 14A. Subsequently, the cathode 13 and the anode 14, which
are formed with the electrolyte 16, are layered with the separator
15 in between. The lamination is wound in the longitudinal
direction and the protective tape 17 is adhered to the outermost
periphery to form the spirally wound electrode body 10. Finally,
for example, the spirally wound electrode body 10 is sandwiched
between the package members 20, and the outer edges of the package
member 20 are contacted by thermal fusion bonding or the like, and
the spirally wound electrode body 10 is enclosed. Then, the
adhesive films 21 are inserted between the cathode lead 11, the
anode lead 12 and the package member 20. The secondary battery
shown in FIGS. 1 and 2 is thereby obtained.
[0057] In the secondary battery, when charged, lithium ions are
extracted from the cathode active material layer 13B and inserted
in the anode active material layer 14B through the electrolyte 16.
Next, when discharged, the lithium ions are extracted from the
anode active material layer 14B, and inserted in the cathode active
material layer 13B through the electrolyte 16. In this embodiment,
the open circuit voltage in full charge is high, 4.25 V or more,
and the vicinity of the cathode 13 is in the strong oxidizing
atmosphere. However, since the electrolyte 16 contains a polymer
containing vinylidene fluoride as a component, oxidation and
decomposition reaction in the vicinity of the cathode 13 is
inhibited.
[0058] As above, in this embodiment, since the open circuit voltage
in full charge per a pair of the cathode 21 and the anode 22 is in
the range from 4.25 V to 6.00 V. Therefore, a high energy density
can be obtained. Further, since the electrolyte 16 contains a
polymer containing vinylidene fluoride as a component, oxidation
and decomposition reaction in the vicinity of the cathode 13 is
inhibited even when the open circuit voltage in full charge is
raised. Consequently, the battery characteristics such as cycle
characteristics can be improved.
EXAMPLES
[0059] Further, specific examples of the present invention will be
described in detail.
Examples 1-1 and 1-2
[0060] Secondary batteries shown in FIGS. 1 and 2 were fabricated.
First, a cathode active material was formed as follows. As an
aqueous solution, commercially available nickel nitrate, cobalt
nitrate, and manganese nitrate were mixed so that the ratios of Ni,
Co, and Mn became 0.333, 0.334, and 0.333, respectively. After
that, while the mixture was sufficiently stirred, ammonia water was
dropped into the mixed solution to obtain a complex hydroxide. The
complex hydroxide and lithium hydroxide were mixed, the mixture was
fired for 10 hours at 900 deg C. in the oxygen air current, and
pulverized to obtain lithium complex oxide powder as a cathode
active material. When the obtained lithium complex oxide powder was
analyzed by Atomic Absorption Spectrometry (ASS), the composition
of LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 was verified.
Further, when the particle diameter was measured by laser
diffraction method, the average particle diameter was 13 .mu.m.
Further, when X-ray diffraction measurement was conducted, it was
confirmed that the measurement result was similar to the pattern of
LiNiO.sub.2 listed in No. 09-0063 of the ICDD (International Center
for Diffraction Data) card, and a bedded salt structure similar to
of LiNiO.sub.2 was formed. Furthermore, when the obtained lithium
complex oxide powder was observed by Scanning Electron Microscope
(SEM), spherical particles in which primary particles being from
0.1 .mu.m to 5 .mu.m in size were agglomerated were observed.
[0061] Next, 86 wt % of the obtained
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 powder, 10 wt % of
artificial graphite powder as an electrical conductor, and 4 wt %
of polyvinylidene fluoride as a binder were mixed. The mixture was
dispersed in N-methyl-2-pyrrolidone as a solvent to obtain cathode
mixture slurry. Subsequently, the both faces of the cathode current
collector 13A made of a strip-shaped aluminum foil being 20 .mu.m
thick were uniformly coated with the cathode mixture slurry, which
was dried and compress-molded by a rolling press machine to form
the cathode active material layer 13B and thereby form the cathode
13.
[0062] Further, spheroidal graphite powder as an anode active
material was prepared. 90 wt % of the spheroidal graphite powder
and 10 wt % of a copolymer of vinylidene fluoride and
hexafluoropropylene as a binder were mixed. The mixture was
dispersed in N-methyl-2-pyrrolidone as a solvent to obtain anode
mixture slurry. Next, the both faces of the anode current collector
14A made of a strip-shaped copper foil being 10 .mu.m thick were
uniformly coated with the anode mixture slurry, which was provided
with hot press molding to form the anode active material layer 14B
and thereby form the anode 14. For the cathode 13 and the anode 14,
the coating amounts of the cathode active material and the anode
active material were adjusted so that the ratio of the theoretical
lithium extraction amount per unit area of the cathode 13 and the
theoretical lithium insertion amount per unit area of the anode 14
opposed to the cathode 13 became cathode/anode=0.95 in a
predetermined charging voltage. Then, the charging voltage was 4.25
V in Example 1-1, and 4.55 in Example 1-2.
[0063] Subsequently, 42.5 wt % of ethylene carbonate, 42.5 wt % of
propylene carbonate, and 15 wt % of LiPF.sub.6 were mixed to
prepare an electrolytic solution. 30 parts by weight of the
electrolytic solution and 10 parts by weight of a block copolymer
of vinylidene fluoride and hexafluoropropylene with the weight
average molecular weight of about 0.6 million were mixed and
dissolved by using a mixed solvent to form a precursor solution.
After that, the both faces of the cathode 13 and the anode 14 were
coated with the precursor solution, the mixed solution was
volatilized, and the electrolyte 16 was respectively formed. Next,
the cathode lead 11 was attached to the cathode current collector
13A, and the anode lead 12 was attached to the anode current
collector 14A.
[0064] Subsequently, the cathode 13 and the anode 14, which are
formed with the electrolyte 16, were layered with the separator 15
made of a microporous polyolefin film in between and wound to form
the spirally wound electrode body 10. After that, the spirally
wound electrode body 10 was sandwiched between the package members
20 made of an aluminum laminated film. The peripheral edges of the
package member 20 were contacted to each other, and the spirally
wound electrode body 10 was enclosed. Thereby, the secondary
batteries of Examples 1-1 and 1-2 were obtained.
[0065] As Comparative examples 1-1 and 1-2 relative to Examples 1-1
and 1-2, secondary batteries were fabricated in the same manner as
in Examples 1-1 and 1-2, except that the electrolytic solution was
directly injected into the package member without using a polymer
containing vinylidene fluoride as a component. Further, as
Comparative examples 1-3 and 1-4, secondary batteries were
fabricated in the same manner as in Examples 1-1 and 1-2, except
that the coating amounts of the cathode active material and the
anode active material were adjusted as the charging voltage of 4.20
V, and further except that in Comparative example 1-4, the
electrolytic solution was directly injected into the package member
without using a polymer.
[0066] For the fabricated secondary batteries of Examples 1-1 and
1-2, and Comparative examples 1-1 to 1-4, charge and discharge were
performed, and the discharge capacity retention ratio of each cycle
to the discharge capacity at the first cycle was examined. Then,
for charging, at 23 deg C., after constant current charge was
performed at a current value at which the theoretical capacity is
wholly discharged in 2 hours until the battery voltage reached a
specific value, constant voltage charge was performed for 5 hours
at a specific constant voltage to obtain a full charge state. The
specific voltage value was 4.25 V in Example 1-1 and Comparative
example 1-1, 4.55 V in Example 1-2 and Comparative example 1-2, and
4.20 V in Comparative examples 1-3 and 1-4. For discharge, at 23
deg C., constant current discharge was performed at a current value
at which the theoretical capacity is wholly discharged in 2 hours
until the battery voltage reached 3.0 V and a full discharge state
was obtained. The obtained results are shown in FIGS. 3 to 5.
[0067] As shown in FIGS. 3 to 5, in Examples 1-1 and 1-2, and
Comparative examples 1-1 and 1-2, in which the charging voltage was
4.25 V or more, lowering of the discharge capacity could be smaller
in Examples 1-1 and 1-2 using the polymer containing vinylidene
fluoride as a component compared to in Comparative examples 1-1 and
1-2 using the electrolytic solution directly. In particular, when
comparing Example 1-2 to Comparative example 1-2, in which the
charging voltage was high, 4.55 V, the discharge capacity retention
ratio could be significantly improved in Example 1-2 than in
Comparative example 1-2. Meanwhile, in Comparative examples 1-3 and
1-4, in which the charging voltage was 4.20 V, the discharge
capacity retention ratios were almost equal to each other
regardless of usage of the polymer.
[0068] That is, it was found that as long as the polymer containing
vinylidene fluoride as a component was used, the oxidation
stability of the electrolyte 16 could be improved, and superior
cycle characteristics could be obtained even when the open circuit
voltage in full charge was 4.25 V or more.
Examples 2-1, 2-2, 3-1, and 3-2
[0069] Secondary batteries were fabricated in the same manner as in
Examples 1-1 and 1-2, except that as a cathode active material,
LiCoO.sub.2 powder was used in Examples 2-1 and 2-2 and
LiCo.sub.0.98Al.sub.0.01Mg.sub.0.01O.sub.2 powder was used in
Examples 3-1 and 3-2; and the predetermined charging voltage was
4.40 V in Example 2-1, 4.55 V in Example 2-2, 4.40 V in Example
3-1, and 4.55 V in Example 3-2.
[0070] As Comparative examples 2-1 and 2-2 relative to Examples 2-1
and 2-2, and as Comparative examples 3-1 and 3-2 relative to
Examples 3-1 and 3-2, secondary batteries were fabricated in the
same manner as in Examples 2-1 and 2-2 or Examples 3-1 and 3-2,
except that the electrolytic solution was directly injected into
the package member without using a polymer containing vinylidene
fluoride as a component. Further, as Comparative examples 2-3 and
2-4, and Comparative examples 3-3 and 3-4, batteries were
fabricated in the same manner as in Examples 2-1 and 2-2 or
Examples 3-1 and 3-2, except that the coating amounts of the
cathode active material and the anode active material were adjusted
as the charging voltage of 4.20 V, and further except that in
Comparative examples 2-4 and 3-4, the electrolytic solution was
directly injected into the package member without using a
polymer.
[0071] For the fabricated secondary batteries of Examples 2-1, 2-2,
3-1, and 3-2, and Comparative examples 2-1 to 2-4 and 3-1 to 3-4,
charge and discharge were performed in the same manner as in
Examples 1-1 and 1-2, and the discharge capacity retention ratio of
each cycle to the discharge capacity at the first cycle was
examined. The specific voltage value in charging was 4.40 V in
Examples 2-1 and 3-1, and Comparative examples 2-1 and 3-1; 4.55 V
in Examples 2-2 and 3-2, and Comparative examples 2-2 and 3-2; and
4.20 V in Comparative examples 2-3, 2-4, 3-3, and 3-4. The obtained
results are shown in Tables 1 and 2, and FIGS. 6 to 9.
TABLE-US-00001 TABLE 1 Discharge capacity Charging Cathode
retention ratio (%) voltage active 100th 200th 400th (V) material
Electrolyte cycle cycle cycle Example 2-1 4.40 LiCoO.sub.2 Polymer
98.6 92.1 84.0 Example 2-2 4.55 contained 90.6 84.0 76.0
Comparative 4.40 LiCoO.sub.2 Without 92.1 59.6 0 example 2-1
polymer Comparative 4.55 88.3 40.1 0 example 2-2 Comparative 4.20
Polymer 99.0 94.4 88.0 example 2-3 contained Comparative Without
98.9 94.0 87.7 example 2-4 polymer
TABLE-US-00002 TABLE 2 Discharge capacity retention ratio (%)
Charging Cathode active 100th 200th 400th voltage (V) material
Electrolyte cycle cycle cycle Example 4.40
LiCo.sub.0.98Al.sub.0.01Mg.sub.0.01O.sub.2 Polymer 97.5 95.4 89.3
3-1 contained Example 4.55 95.7 92.1 87.2 3-2 Comparative 4.40
LiCo.sub.0.98Al.sub.0.01Mg.sub.0.01O.sub.2 Without 92.4 62.5 0
example polymer 3-1 Comparative 4.55 90.3 41.4 0 example 3-2
Comparative 4.20 Polymer 99.1 95.0 90.0 example contained 3-3
Comparative Without 99.0 94.2 88.6 example polymer 3-4
[0072] As shown in Tables 1 and 2, as in Examples 1-1 and 1-2, in
the case that the charging voltage was over 4.20 V, the discharge
capacity retention ratio could be significantly improved in
Examples 2-1, 2-2, 3-1, and 3-2 using the polymer containing
vinylidene fluoride as a component than in Comparative examples
2-1, 2-2, 3-1, and 3-2 using the electrolytic solution directly.
Meanwhile, in Comparative examples 2-3, 2-4, 3-3, and 3-4, in which
the charging voltage was 4.20 V, the discharge capacity retention
ratios were almost equal to each other regardless of usage of the
polymer.
[0073] That is, it was found that as long as the polymer containing
vinylidene fluoride as a component was used, similar effect could
be obtained even when other cathode active material was used.
Examples 4-1 to 4-10, 5-1 to 5-9, 6-1, and 6-2
[0074] Secondary batteries were fabricated in the same manner as in
Examples 1-1 and 1-2, except that in Examples 4-1 to 4-9, as a
cathode active material, a mixture of LiCoO.sub.2 powder and
LiNi.sub.0.33CO.sub.0.33Mn.sub.0.33O.sub.2 powder was used and the
predetermined charging voltage was 4.40 V, and except that in
Example 4-10, as a cathode active material,
LiNi.sub.0.33CO.sub.0.33Mn.sub.0.33O.sub.2 powder was used and the
predetermined charging voltage was 4.40 V.
[0075] In Examples 5-1 to 5-9, secondary batteries were fabricated
in the same manner as in Examples 1-1 and 1-2, except that as a
cathode active material, a mixture of LiCoO.sub.2 powder and
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 powder was used and the
predetermined charging voltage was 4.55 V.
[0076] In Examples 6-1 and 6-2, secondary batteries were fabricated
in the same manner as in Examples 1-1 and 1-2, except that as a
cathode active material, a mixture of
Li.sub.0.98Al.sub.0.01Mg.sub.0.01O.sub.2 powder and
LiNi.sub.0.33CO.sub.0.33Mn.sub.0.33O.sub.2 powder was used and the
predetermined charging voltage was 4.40 V or 4.55 V.
[0077] For the fabricated secondary batteries of Examples 4-1 to
4-10, 5-1 to 5-9, and 6-1 to 6-2, charge and discharge were
performed in the same manner as in Examples 1-1 and 1-2, and the
discharge capacity retention ratio of each cycle to the discharge
capacity at the first cycle was examined. The predetermined voltage
value in charging was 4.40 V in Examples 4-1 to 4-10 and 6-1; and
4.55 V in Examples 5-1 to 5-9 and 6-2. The obtained results are
shown in Tables 3 to 5 together with the results of Examples 1-2,
2-1, 2-2, 3-1, and 3-2.
TABLE-US-00003 TABLE 3 Charging voltage: 4.40 V Discharge capacity
Composition of cathode active retention ratio (%) material (weight
ratio) 100th 200th 400th LiCoO.sub.2
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 cycle cycle cycle
Example 10 0 98.6 92.1 84.0 2-1 Example 9 1 98.8 91.8 84.0 4-1
Example 8 2 98.3 91.7 83.9 4-2 Example 7 3 98.0 91.7 84.3 4-3
Example 6 4 98.1 91.9 84.5 4-4 Example 5 5 97.9 92.0 84.6 4-5
Example 4 6 98.6 91.8 84.5 4-6 Example 3 7 98.0 92.1 84.7 4-7
Example 2 8 98.4 92.0 84.6 4-8 Example 1 9 98.3 92.4 84.8 4-9
Example 0 10 98.5 93.0 84.9 4-10
TABLE-US-00004 TABLE 4 Charging voltage: 4.55 V Discharge capacity
Composition of cathode active retention ratio (%) material (weight
ratio) 100th 200th 400th LiCoO.sub.2
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 cycle cycle cycle
Example 10 0 90.6 84.0 76.0 2-2 Example 9 1 90.6 84.3 76.2 5-1
Example 8 2 90.9 84.0 76.1 5-2 Example 7 3 91.1 84.8 76.8 5-3
Example 6 4 92.2 85.1 77.6 5-4 Example 5 5 92.1 85.2 77.3 5-5
Example 4 6 92.7 85.8 78.6 5-6 Example 3 7 93.1 87.0 79.9 5-7
Example 2 8 93.8 87.9 81.0 5-8 Example 1 9 94.3 90.0 81.5 5-9
Example 0 10 94.7 90.2 82.0 1-2
TABLE-US-00005 TABLE 5 Discharge capacity Charging Composition of
cathode active material retention ratio (%) voltage (weight ratio)
100th 200th 400th (V) LiCo.sub.0.98Al.sub.0.01Mg.sub.0.01O.sub.2
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 cycle cycle cycle
Example 4.40 10 0 97.5 95.4 89.3 3-1 Example 7 3 96.9 94.5 89.6 6-1
Example 4.55 10 0 95.7 92.1 87.2 3-2 Example 7 3 96.1 93.5 86.0
6-2
[0078] As shown in Tables 3 to 5, even when the mixture of cathode
active materials was used, results equal to of Examples 1-2, 2-1,
2-2, 3-1, and 3-2, in which one cathode active material was singly
used could be obtained. That is, it was found that as long as the
polymer containing vinylidene fluoride as a component was used,
similar effect could be obtained even when the mixture of cathode
active materials was used.
[0079] The present invention has been described with reference to
the embodiment and the examples. However, the present invention is
not limited to the foregoing embodiment and the foregoing examples,
and various modifications may be made. For example, in the
foregoing embodiment and the foregoing examples, descriptions have
been given of the case using lithium as an electrode reactant.
However, the present invention can be applied to the case using
other Group 1A element such as sodium (Na) and potassium (K), a
Group 2A element such as magnesium and calcium (Ca), other light
metal such as aluminum, or an alloy of lithium or the foregoing as
well, and similar effects can be thereby obtained. Then, for the
anode active material, the anode material as described in the
foregoing embodiments can be similarly used.
[0080] Further, in the foregoing embodiment and the foregoing
examples, descriptions have been given of the case, in which the
separator 15 and the electrolyte 16 are provided between the
cathode 13 and the anode 14. However, when sufficient insulation
can be secured by, for example, mixing an insulative filler with an
electrolyte, the separator 15 may be omitted.
[0081] Further, in the foregoing embodiment and the foregoing
examples, descriptions have been given of the secondary battery
having a spirally wound structure, in which the cathode 13 and the
anode 14 are layered and wound. However, the present invention can
be similarly applied to the secondary battery having a structure in
which a cathode and an anode are folded, or a structure in which a
cathode and an anode are layered. In addition to the film package
member, a can package member can be also used. Further, the present
invention can be similarly applied to a secondary battery such as a
so-called coin type secondary battery, a button type secondary
battery, a cylinder type secondary battery, and a square type
secondary battery. Furthermore, the present invention can be
applied to primary batteries in addition to the secondary
batteries.
[0082] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alternations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
* * * * *